1. Field of the Invention
The present invention relates to a droplet ejection device which ejects droplets.
2. Description of Related Art
A known droplet ejection device which ejects droplets is an inkjet recording apparatus which records a letter or an image on a recording medium by ejecting from nozzles droplets of ink to a recording medium such as a recording sheet. Such an inkjet recording apparatus, in general, is provided with an inkjet head having a carriage capable of making a back-and-forth movement in a direction orthogonal to the conveyance direction of the recording sheet and nozzles formed on the carriage. The inkjet recording apparatus records text or an image on a recording sheet by ejecting ink from at least one of the nozzles on the inkjet head, while moving the carriage.
The inkjet head of the inkjet recording apparatus however has the following problem. Namely, when the inkjet head is left for a long time without performing recording: that is, the state of not ejecting ink from the nozzle lasts for a long time, the ink inside the nozzle dries, and may cause a clogging in the nozzle. Even if the printing is performed, an inkjet recording apparatus using more than one type of ink has a problem that there is a nozzle which frequently ejects ink and a nozzle which rarely ejects ink, depending on the type of ink. In the inkjet recording apparatus, new ink is successively supplied to the nozzle frequently ejecting ink and therefore clogging in such a nozzle hardly occurs. However, in the nozzle which rarely ejects ink, new ink is rarely supplied. Therefore, the ink in the nozzle more easily dries up, consequently causing a clogging in the nozzle.
To solve the above problem, a flushing operation is performed in some cases. Specifically, an ink receiver is provided outside a recording sheet conveyance path, and a carriage is moved so as to bring the inkjet head in a position where the inkjet head faces the ink receiver. Then, ink is ejected from each of the nozzles to the ink receiver, so as to discharge highly viscous ink inside the nozzle. The ink discharged through this flushing operation adheres to and is absorbed by an absorber provided to the ink receiver.
Note that a plurality of types of ink ejected to the ink receiver through the above flushing operation includes a type of ink which easily solidifies. When such an easily-solidifiable ink adheres to the ink receiver, a highly-vaporizable solvent in the ink vaporizes before the ink is absorbed into the absorber. As a result, the ink adheres and solidifies on the surface of the absorber. When ink droplets are further ejected from the nozzles in the subsequent flushing operation while the absorber has thereon solidified ink, the ejected ink further adheres and solidifies on the solidified ink. Repeating this deposits solidified ink on the absorber, thus forming a pile of solidified ink. This leads to a problem that the lower surface (nozzle) of the inkjet head contacts the deposition of the ink, when the inkjet head moves along with the carriage to perform the flushing operation.
To solve this, Japanese Unexamined Patent Publication No. 168177/2006 (Tokukai 2006-168177) discloses a droplet ejection device in which low viscous ink which hardly thickens (hardly solidifiable ink) is landed on highly viscous ink which easily thickens (easily solidifiable ink) and which adhered on the ink receiver at the time of flushing operation, thereby dissolving the ink adhered on the ink receiver.
However, in the droplet ejection device of the above publication, nozzles (N7 in the publication) which eject hardly solidifiable ink for dissolving the adhered ink are closer to a printing region in the moving direction of the carriage, compared to nozzles (N4 and N5 in the publication) which eject easily solidifiable ink. To dissolve the deposition of easily solidifiable ink adhered on the surface of the ink receiver, the carriage needs to be further moved from the flushing region, towards a direction opposite to the printing region (towards outside of the apparatus), so that the nozzles (N7) for ejecting the hardly-solidifiable ink are outside the ink receiver (left end in FIG. 1 of the publication). This causes an increase in the size of the apparatus.